This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-244762 filed on Aug. 11, 2000.
1. Field of the Invention
The present invention relates to a solder-bonding structure of a terminal and also to a brushless motor including the terminal having one end connected to exciting coils and the other end solder-bonded to a circuit board through the solder-bonding structure.
2. Description of Related Art
One type of brushless motor used, for example, as a blower motor of a vehicle air conditioning system includes a stator and a circuit board. The stator includes exciting coils, and the circuit board includes an excitation circuit. A power supply terminal for supplying electric power to the exciting coils is electrically connected to the excitation circuit of the circuit board through a connector terminal. One previously proposed structure for connecting the connector terminal to the excitation circuit of the circuit board is shown in FIGS. 16 to 19.
As shown in FIG. 16, an elongated hole 52 penetrates through the circuit board 51, and conductors 53 are provided around opposed open ends of the elongated hole 52, respectively (FIGS. 18 and 19). As shown in FIGS. 16-17B, the connector terminal 54 includes a fitting portion 55, a bonding portion 56 and a bridge 57. The fitting portion 55 is fitted to or electrically connected to the power supply terminal (not shown) that is, in turn, connected to the exciting coils. The bonding portion 56 is received within the elongated hole 52 and is solder-bonded to the conductors 53. The bridge 57 electrically connects between the fitting portion 55 and the bonding portion 56. With the above arrangement, the exciting coils are electrically connected to the excitation circuit through the connector terminal 54 and the conductors 53.
With reference to FIG. 17A, the elongated hole 52 is formed to receive the plate-shaped bonding portion 56 therein. As shown in FIGS. 16 and 17B, a couple of positioning projections 56a are provided on opposed ends of the bonding portion 56, respectively. The positioning projections 56a abut against the circuit board 51 and determine a position of the bonding portion 56 in an insertion direction of the bonding portion 56. At the center of the bonding portion 56, a slit 56b is provided as a through hole that penetrates through a portion of the bonding portion 56 and a portion of the bridge 57. More specifically, when the bonding portion 56 is inserted to a predetermined position in the elongated hole 52, the slit 56b extends from the bridge 57 to about one half the depth of the elongated hole 52 of the circuit board 14.
As shown in FIG. 18, after the bonding portion 56 is inserted through the elongated hole 52, the bonding portion 56 is solder-bonded to the conductors 53. This solder-bonding is conducted as follows. That is, a solder material (not shown) is applied to one flat surface 56c (located on the left side in FIG. 18) of a base end side region (where the slit 56b is formed) of the bonding portion 56. Then, a soldering iron (not shown) is applied against the other flat surface 56d (located on the right side in FIG. 18) of the bonding portion 56 to melt the solder material. During this solder-bonding process, melted solder material flows through a flow passage 58 formed by the slit 56b toward an opposite side of the bonding portion 56 in a direction perpendicular to the bonding portion 56. Furthermore, the melted solder material also flows toward an opposite side of the circuit board 51 (toward the distal end side of the bonding portion 56) through spaces 59a, 59b formed between the bonding portion 56 and wall surfaces of the elongated hole 52 when the bonding portion 56 is inserted through the elongated hole 52 and is positioned in the center of the cross-section of the elongated hole 52. In this way, the bonding portion 56 is solder-bonded to the conductors 53.
However, it may happen that the bonding portion 56 is not positioned in the center of the elongated hole 52 due to, for example, size variation or positioning error of the connector terminal 54 and/or the circuit board 51 (FIG. 19). If the solder-bonding is conducted while the flat surface 56d is engaged with wall surface 52a extending in a horizontal direction of the cross-section of the elongated hole 52, the melted solder material is restrained from flowing toward the distal end side of the flat surface 56d of the bonding portion 56. Thus, as shown in FIG. 19, the solder material is accumulated on the distal end side of the flat surface 56c of the bonding portion 56, so that the distal end side of the flat surface 56d of the bonding portion 56 is not solder-bonded to the conductor 53. As a result, bonding strength of the solder-bonded portion is weakened. Especially, in the case of the brushless motor or the like, the connector terminal 54 is connected to the stator, so that the solder-bonded portion can be easily damaged (easily cracked) by vibrations of the stator. In order to avoid this, the distal end side of the bonding portion 56 can be first solder-bonded to the conductor 53 prior to solder-bonding the rest of the bonding portion 56. However, this will disadvantageously lengthen the solder-bonding operation.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a solder-bonding structure of a terminal that allows easy and proper solder-bonding thereof. It is another objective of the present invention to provided a brushless motor having such a solder-bonding structure of the terminal.
To achieve the objectives of the present invention, there is provided a solder-bonding structure including a circuit board and a plate-shaped terminal. The circuit board has an elongated hole penetrating through the circuit board. The elongated hole is provided with two conductors arranged around opposed open ends of the elongated hole, respectively. The plate-shaped terminal is arranged to be received through the elongated hole of the circuit board and to be solder-bonded to the conductors. The terminal includes at least one flow-passage defining portion that defines at least one flow passage. The at least one flow passage allows flow of melted solder material therethrough in a direction that is generally parallel to a plane of the circuit board and also in a direction that is generally perpendicular to a plane of the circuit board. Alternatively or additionally, the at least one flow passage may allow flow of melted solder material from one of opposed sides of the terminal to the other of opposed sides of the terminal within the elongated hole and may also allows flow of the melted solder material along each one of opposed wall surfaces of the elongated hole from one of the open ends of the elongated hole to the other of the open ends of the elongated hole even when one of the opposed sides of the terminal abuts against one of the opposed wall surfaces of the elongated hole.
There is also provided a brushless motor that includes a stator and a solder-bonding structure. The stator has a plurality of exciting coils. The solder-bonding structure includes a circuit board and a plate-shaped terminal. The circuit board has an excitation circuit for supplying electric current to the plurality of exciting coils. The circuit board has an elongated hole that penetrates through the circuit board. The elongated hole is provided with two conductors arranged around opposed open ends of the elongated hole, respectively. The plate-shaped terminal is electrically connected to the plurality of exciting coils. The terminal is arranged to be received through the elongated hole of the circuit board and to be solder-bonded to the conductors. The terminal includes at least one flow-passage defining portion that defines at least one flow passage. The at least one flow passage allows flow of melted solder material therethrough in a direction that is generally parallel to a plane of the circuit board and also in a direction that is generally perpendicular to a plane of the circuit board.